JP1997(09)-133202 (FIG. 1, paragraph 0013) suggests a lubricating mechanism for a transfer. A casing houses, therein, the transfer, the lubricating mechanism and so on. In response to rotation of a chain, or of a sprocket, which contributes to power distribution, a lubricant is agitated and adhered to an inner surface of the casing. The adhered lubricant runs down on the inner surface of the casing and is partially introduced, through an oil groove formed at a rear case of the casing, to a space behind a bearing, i.e., to a clearance between a bearing and an oil seal. Accordingly, the lubricating mechanism can lubricate the bearing and the oil seal.
FIG. 3 is a partially cross sectional view for explaining a lubricating mechanism for a transfer associated with the conventional work.
With reference to FIG. 3, the transfer associated with the conventional work includes: a rotational shaft 11; a casing 12 housing the rotational shaft 11 and so on therein; a bearing 15 interposed between the rotational shaft 11 and the casing 12 and freely rotatably supporting the rotational shaft 11; an oil seal 14 provided between the casing 12 and an output member 18 in a space that is inside the casing 12 and behind (the right side in FIG. 3) the bearing 15; a sprocket 16 fitted on the rotational shaft 11 ahead of (the left side in FIG. 3) the bearing 15 and contributing in power distribution; the output member 18 spline-engaged with the rotational shaft 11 behind the bearing 15 and contributing in power distribution; and a washer 17 interposed between the sprocket 16 and the bearing 15. The bearing 15 is fitted at its inner race 15a on the rotational shaft 11, while an outer race 15b of the bearing 15 is provided at a radially extending wall of the casing 12.
The lubricating mechanism for a transfer associated with the prior art illustrated in FIG. 3, especially the lubricating mechanism by which a lubricant is guided and introduced to the oil seal 14, includes: an axial oil passage 11a formed inside the rotational shaft 11 so as to extend axially from a front side of the bearing 15 towards the bearing 15; a radial oil passage 11b formed inside the rotational shaft 11 so as to extend radially ahead of the bearing 15, one side of the radial oil passage 11b communicating with the axial oil passage 11a and the other side thereof opening at an outer peripheral surface of the rotational shaft 11 ahead of the bearing 15; a sprocket inner peripheral side oil passage 11c provided so as to extend between the outer peripheral surface of the rotational shaft 11 and an inner peripheral surface of the sprocket 16, one side of the sprocket inner peripheral side oil passage 11c communicating with the other opening side of the radial oil passage 11b and the other side of the sprocket inner peripheral side oil passage 11c communicating with a clearance between the sprocket 16 and the washer 17; and an oil receiver 13 through which a front space 10a, which is defined above (an upper side in FIG. 3) the washer 17, is connected to a rear space 10b. 
According to the lubricating mechanism illustrated in FIG. 3, a lubricant, which is conveyed to the sprocket inner peripheral side oil passage 11c through the axial oil passage 11a and the radial oil passage 11b, is subjected with a centrifugal force in response to rotation of the washer 17 and scatters radially outwardly through a clearance between the sprocket 16 and the washer 17. The oil receiver 13 then receives the scattered lubricant. The lubricant received by the oil receiver 13 runs down on an inner surface of the casing 12 and is supplied to the oil seal 14.
According to the lubricating mechanism illustrated in JP1997(09)-133202 or the lubricating mechanism illustrated in FIG. 3, a lubricant is supplied to the oil seal indirectly, i.e., through the oil groove or the oil receiver which is provided at a radially distant from the rotational shaft. Further, because each lubricating mechanism requires the oil groove or the oil receiver, the structure of the lubricating mechanism may become complicated.
The present invention has been made in view of the above circumstances, and provides a lubricating mechanism, which is configured with a simple and highly robust structure and can supply lubricant directly to a lubrication required portion, such as an oil seal, with high reliability.